A great many motor driven pumps assemblies are known in the art for pumping hazardous or corrosive fluids. In particular, care must be taken in the design of the pump and in the design of the mechanism coupling its drive shaft to a motor to insure that such fluids do not leak into the exterior environment to produce a hazard to attendant personnel. This poses severe requirements on the corrosion resistance of pump materials, and in particular on the corrosion and wear resistance of pump drive shaft seals. One successful approach has been to provide the driven end of the pump drive shaft with a generally radially extending carrier structure rigidly affixed to the shaft end. Embedded within the carrier structure are a plurality of permanent magnets, typically in the form of elongated bars, having one of their major dimensions closely proximate to the external periphery of the carrier. The carrier is made of material not susceptible to attack by the fluid being pumped. The housing is in turn configured with a generally closely fitting cylindrical containment shell or shroud sealed at one end and closely confining the carrier, the shell being sealed at its other end to the housing.
Motor drive power is supplied through a similar magnet-carrying assembly having a generally cylindrical collar coaxially disposed with respect to, and extending over the containment shell and having a similar number of permanent magnets affixed to the interior surface thereof. Rotation of the outer magnet assembly will then cause the interior magnets to be drawn into rotation generally in synchronism with the speed of the drive motor. Such systems are well known in the art, and are shown, for example, in Oikawa U.S. Pat. No. 4,013,384, the contents of which are incorporated by reference herein. A principal problem with such structures is that the containment. shell, which must necessarily have relatively thin outer walls to keep the inter-magnet spacing at a minimum may on occasion crack, resulting in hazardous leakage. To the applicant's knowledge there has not been a satisfactory solution to this problem to date.
The teachings of the present invention are oriented towards a solution of this problem.